Radiation collimator

ABSTRACT

A radiation collimator including opposed pairs of movable offfocus radiation diaphragms comprising interleaved arrays of plates supported centrally on stems. The stems of each opposed pair of diaphragms are pivotally supported and coupled together for concurrent movement toward and away from each other. Each opposed pair of off-focus diaphragms is interconnected to corresponding on focus diaphragms movably mounted for rectangularly delineating the perimeter of the primary beam. The off-focus diaphragms extend to within very close proximity of the radiation source to block off-focus radiation.

United States Patent [191 Aug. 13, 1974 Hura [ 1 RADIATION COLLIMATOR[75] Inventor: Michael Hura, Wickliffe, Ohio [73] Assignee: PickerCorporation, Cleveland,

Ohio

[22] Filed: Jan. 29, 1973 [21] Appl. No.: 327,644

[52] US. Cl. 250/511, 250/513 [51] 1nt.C1. G031) 41/16 [58] Field ofSearch 250/511, 512, 513

[56] References Cited UNITED STATES PATENTS 1,738,945 12/1929 Brenbert250/512 1,909,118 5/1933 Raab 250/513 3,023,314 2/1962 Hura 250/4393,448,270 6/1969 Peyser 250/513 3,609,370 9/1971 Peyser 250/511 PrimaryE.\'aminer.lames W. Lawrence Assistant Examiner-C. E. Church Attorney,Agent, or FirmWatts, Hoffmann, Fisher & Heinke Co.

[ 5 7 ABSTRACT A radiation collimator including opposed pairs of movableoff-focus radiation diaphragms comprising interleaved arrays of platessupported centrally on stems. The stems of each opposed pair ofdiaphragms are pivotally supported and coupled together for concurrentmovement toward and away from each other. Each opposed pair of off-focusdiaphragms is interconnected to corresponding on focus diaphragmsmovably mounted for rectangularly delineating the perimeter of theprimary beam. The off-focus diaphragms extend to within very closeproximity of the radiation source to block off-focus radiation.

25 Claims, 9 Drawing Figures PATENTEDAIJ: 1 3 an ill PATENTEDAUB1-3l9743.829.101

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RADIATION COLLIMATOR CROSS REFERENCE TO RELATED PATENT X-Ray Apparatus,U.S. Pat. No. 3,023,314, issued Feb. 27, 1962 to Michael Hura.

BACKGROUND OF THE INVENTION 1. Field of the Invention The presentinvention relates generally to X-ray apparatus and more particularly to'a collimator structure designed to block undesired off-focus radiation.

2. Prior Art In radiographic studies, an X-ray film is exposed byradiation emanating from an X-ray tube. It is desirable to confine theX-radiation to the area of the subject under examination not only tominimize the exposure of the patient and attending persons to theprimary beam, but also to minimize radiation scatter effects.

Radiation scatter is produced when the primary radiation beam strikes apatient or object and is diffracted. If the size of the X-ray beam islarger than required to accommodate a particular area underinvestigation, the X-radiation striking areas of the subject around thearea of investigation will produce an unnecessary amount of radiationscatter which has the effect of fogging the radiograph thereby producinga poor image.

Mechanisms known as collimators are used to delineate an X-ray beam ofthe desired size. In radiographic examinations, these collimatorsgenerally include two pairs of relatively movable diaphragms whichdelineate an X-ray beam of rectangular cross section. Thesediaphragms,when properly adjusted, will minimize scatter, but by no means elimateall causes of blurred radiographs. The X-ray beam is emitted from a verysmall area on an X-ray tube anode known as the focal spot.Theoretically, this spot can be so small and bombardment of it withelectrons so precise that the beam is emitted in a precise and regularconical pattern of onfocus radiation. As a practical matter, the spot isa larger area than a theoretically optimized spot and an X-ray tubeemits a penumbra or band of so-called offfocus radiation from areasaround the spot. The collimator diaphragms are typically spaced fromabout four to about eleven inches from the X-ray tube focal spot. Withthis spacing, some off-focus radiation comingles with the on-focusradiation with a resultant blurring of the radiograph.

Mechanisms for adjusting the diaphragms are typically positioned,speaking transversely of the beam, between the diaphragms and the focalspot. The mechanisms are offset from the primary beam so that they donot interfere with it. The off-focus radiation, however, is notnecessarily absorbed by the diaphragms provided to delineate the beamsize, but rather may spread outwardly from the theoretical beam. To theextent that radiation which comingles with the primary beam can causeserious degradation in radiographic quality.

Attempts have been made to control this off-focus radiation but nonehave been fully successful. The problems in properly controllingoff-focus radiation are that:

l. The mechanism for controlling the off-focus radiation should notinterfere with the desired on-focus radiation in the primary beam, butat the same time should absorb all radiation around the primary beam;

2. Since the area of the primary beam is adjustable both longitudinallyand transversely, the off-focus device should desirably be adjustablewith the onfocus diaphragms of the collimator;

3. With the limited space available, providing a rectangular offfocusdevice which is adjustable in both transverse and longitudinaldirections and which does not leak radiation is an objective which hasnot been achieved in the prior art.

One proposal has been to provide a pair of diaphragms fixed in onedirection and a second pair of diaphragms which are adjustable inanother direction. The fixed diaphragms obviously must be positioned tocorrespond to the maximum opening of the on-focus diaphragms.Accordingly, at anything other than a maximum-size radiograph, theoff-focus mechanism does not function to the desired level ofeffectiveness.

Attempts have been made at providing rectangular off-focus collimationwith both longitudinal and transverse adjustment, but all such attemptshave leaked radiation.

Other proposals have been to utilize an iris-type diaphragm whichdelineates a generally circular hole. Since the on-focus diaphragmsdelineate a rectangle, it will be apparent that there must be off-focusradiation around the rectangle or the full rectangular area of the filmcannot be exposed when an iris is used.

SUMMARY OF THE INVENTION Each of the off-focus diaphragm structuresincludes an array of vanes supported by a stem at axially spacedpositions along the X-ray beam path. The vanes of each diaphragmstructure are interleaved on a one-to-one basis with the vanes of twoadjacent diaphragm structures. The supporting stems are pivotallymounted such that the vanes of one pair of diaphragm structures aremovable inwardly and outwardly of the vanes of the other pair ofdiaphragm structures.

The inner edges of the vanes are of straight-line configuration andpositioned such that the diaphragm structures cooperate with theon-focus diaphragms to rectangularly collimate the beam. One vane ofeach of the diaphragm structures, hereinafter called the upper vane,extends into very close proximity to the output window of the X-raytube. Others of the vanes, hereinafter called the lower vanes, arespaced along the beam path and define progressively larger rectangularapertures.

In accordance with one feature of the invention, the sides of the vanesfacing toward the X -,ray beam, hereinafter called the inner sides, areinclined relative to the beam path to prevent radiation scatter. Theinner side inclination is such that the upper surface of each vaneextends inwardly toward the beam path a greater distance than the lowersurface. By this arrangement, the upper surface and the inner side ofeach vane define the beam delineating edge of the vane. Since radiationdoes not ordinarily strike the inner sides of the vanes, there is noresulting radiation scatter.

In accordance with another feature of the present invention, the uppervane of each off-focus diaphragm structure is cocked relative to itssupporting stem in order to keep the inner, beam delineating vane edgeat a relatively constant distance from the output window of the X-raytube as the diaphragm pivots inwardly and outwardly. By thisarrangement, a minimal clearance can be provided between the upper vanesand the X-ray tube output window, and the upper vanes will retainsubstantially the same clearance regardless of the position of theoff-focus diaphragms.

The vanes have curved outer sides which give the assembled off-focuscollimation system a generally circular cross section. The upper vanesare of smaller crosssectional area than are the lower vanes. The lowervanes increase in cross-sectional area the farther removed they are fromthe X-ray source. Accordingly, the assembled off-focus system has agenerally conical outer appearance and is of minimal size in regionsadjacent the X-ray source.

The interleaved vanes have been shown to be effective to block off-focusradiation without substantial radiation leakage. The pivotal mounting ofthe supporting stems at positions removed from the X-ray source providesa construction wherein substantially only the effective area of thevanes themselves extend into regions adjacent the X-ray tube, while thelinkages which connect with the on-focus diaphragms to effect concurtheaccompanying drawings.

BRIEF DESCRIPTIONOF THE DRAWINGS FIG. 1 is a partially schematiccross-sectional view of a radiation collimator constructed in accordancewith the present invention and mounted on an X-ray tube housing;

FIG. 2 is a partially schematic cross-sectional view as seen fromtheplane generally indicated by the broken line 22 in FIG. 1;

FIGS. 3 and 4 are schematic illustrations of the offfocus radiationproblem and illustrating how the present invention operates to greatlyreduce off-focus radiation;

FIG. 5 is an enlarged top plan view of the off-focus collimation portionof the collimator of FIGS. 1 and 2;

FIG. 6 is a side-elevational view of the mechanism shown in FIG. 5 onthe same scale as FIG. 5; and,

FIGS. 7, 8 and 9 are enlarged side, end and top plan views of one of thediaphragm structures incorporated in the mechanism of FIGS. 5 and 6,FIG. 7 being enlarged to a greater degree than are FIGS. 8 and 9.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 and 2, anX-ray apparatus is shown including an X-ray tube housing 10 whichsupports and houses an X-ray tube 11. The X-ray tube 11 has an anode 12.In use, the anode 12 includes a small area known as a focal spot 13which is bombarded with electrons to cause the emission of X-radiationalong a conical beam path 14. I

A collimator 20 is supported by the tube housing 10 around the beam path14. The collimator 20 delineates the perimeter of the beam to arectangular cross section. The collimator 20 includes a housingstructure 21 defining spaced input and output ends 22, 23. Opposed pairsof diaphragm plates 24 are supported on pivotally mounted arms. The armsare mounted in the collimator housing 21 for delineating the perimeterof the X-ray beam. The diaphragm arrangement 24 is of the type disclosedin the referenced patent, and will be described in greater detail.

An off-focus collimation system 25 is interposed be-' tween thediaphragm arrangement 24 and the X-ray tube 11. As will be described ingreater detail, the offfocus collimation system includes two pairs ofmovable diaphragm structures which interconnect with the diaphragmarrangement 24. The off-focus collimation system 25 cooperates with thediaphragm arrangement 24 to block off-focus radiation.

The diaphragm arrangement 24 comprises two pairs of upper diaphragmplates 30, 31 and 32, 33 and two pairs of lower diaphragm plates 34, 35and 36, 37. The upper diaphragm plates 30, 31, 32, 33 are supported,respectively, by arms 40, 41, 42, 43. The lower diaphragm plates 34, 35,36, 37 are supported, respectively, by arms 44, 45, 46, 47. The arms 40,41, 42, 43, 44, 45, 46, 47 are pivotally mounted by stub shafts 50, 51,52, 53, 54, 55, 56, 57 which in turn carry gears 60, 61, 62, 63, 64, 65,66, 67. The gears 60, 61, 64, 65 are meshed as shown in FIG. 1 toprovide for concurrent movement of the diaphragm plates 30, 31, 34, 35.The gears 62, 63, 66, 67 are meshed as shown in FIG. 3 to provideconcurrent movement of the diaphragm plates 32, 33, 36', 37. The gear 65rotates clockwise as seen in FIG. I when the diaphragm plates 30, 31,34, 35 move toward each other, and counterclockwise as these diaphragmsplates move apart. The gear 67 rotates clockwise as seen in FIG. 2 whenthe diaphragm plates 32, 33, 36, 37 move toward each other, andcounterclockwise as these diaphragm plates move apart. Such a diaphragmarrangement is described in greater detail in the referenced patent.

The off-focus collimation system 25 makes connection with the gears 65,67 in order to provide for concurrent movement of the off-focusdiaphragms and the diaphragms 30-37. These connections include projec-The off-focus collimation system 25 principally includes two pairs ofdiaphragm structures 80, 81 and 82, 83. The diaphragm structures 80, 81,82, 83 are pivotally mounted on pairs of stub-shafts 90, 91, 92, 93

which also respectively mount gears 100, 101, 102, "103. The gears 100,101 are meshed to effect concurrent movement of the diaphragm structures80, 81 while the gearsl02, 103 are meshed to effect concurrent movementof the diaphragm structures 82, 83.

As shown in FIG. 5, the control lever 72 connects respectively with oneof the stub shafts 90 while the control lever 73 connects with one ofthe stub shafts 93. By

' this arrangement, the stub shafts 90, 93 pivotally mount the controllevers 72, 73 to interconnect the off-focus diaphragm structures80, 81for concurrent movement with the diaphragms 30, 31, 34, 35, and theoff-focus diaphragm structures 82, 83 for concurrent movement with thediaphragms 32, 33, 36, 37.

Each of the diaphragm structures 80, 81, 82, 83 comprises an array ofvanes supported on a centrally located'stem. Referring to FIGS. 7-9, thediaphragm structure 82 is-shown in greater detail as including an arrayof three vanes .84, 85, 86 supported in cantilever fashion from anintegrally formed, centrally located stem 87. The stem 87 is providedwith a mounting flange 88. A U-shaped bracket 95 is rigidly secured nearthe distal ends of its legs to the stub shafts 93, and is fastened bymeans of threaded fasteners 96. to the mounting flange 88.

The vanes 84, 85, 86 are bounded by planar inner sides84a, 85a, 86a andcurved outer sides 84b, 85b, 86b. The inner sides 84a, 85a, 86acooperate withthe upper surfaces 84c, 85c, 86c of the vanes 84, 85, 86to define beam delineating edges 84d, 85d, 86d. The inner sides 84a,85a, 86a are inclined relative to the beam path to prevent their beingstruck by radiation in such 1 fashion as would produce scatter. The beamdelineating edges 84d, 85d, 86d cooperate with corresponding beamdelineating edges on the diaphragm structures 80, 81, 82, 83 todelineate the beam perimeterto a rectangular cross-section, as best seenin the top view of FIG. 5. The curvedouter sides 84b, 85b, 86b and thecorresponding outer sides of the vanes of the diaphragm structures 80,81, 82, 83 minimize the area occupied by the diaphragm structures topermit their extension into the X-ray tube housing 10 into closeproximity to the X-ray tube 11.

The vanes on the opposed pairs of diaphragm structures 80, 81, and 82,83 are arranged to interleave as shown in FIGS. 1, 2 and 6. Specifcally, the vanes of the diaphragm structures 80, 81 underlie thecorrespond-.

The upper vanes of allof the diaphragm structures 80, 81, 82, 83 arecocked at an angle relative to their respective supporting stems inorder to keep the inner beam delineating edges, e.g. edge 84d, at asubstantially constant, minimal distance from the output window of theX-ray tube-As the diaphragm structures are pivoted inwardly andoutwardly, the cocked upper vanes keep their beam delineating inneredgesin close proximity to the X-ray tube window.

Referring to the schematic illustrations of FIGS. 3 and 4, the diaphragmarrangement 24 principally serves to delineate the perimeter of thebeamof onfocus radiation which emanates from the anode focal spot 13 confinethe on-focus radiation to a selected examination area 15. Off-focusradiation emanating from anode locations spaced from the focal spot 13can pass between the plates of the diaphragm arrangement 24 as shown inFIG. 3 so as to flood an area 16 which includes, but is substantiallylarger than, the examination area-15. The off-focus radiation whichfalls outside the examination area results in an undesirable andentirely useless exposure of the patient to radiation. The offfocusradiation which falls within the examination area 15 tends to overexposeradiographs and to blur the images thereon.

Referring to FIG. 4, in accordance with the present invention, theoff-focus collimation system 25 is provided having movable interleavedvanes which, as described, extend within close proximity of the X-raytube to block off-focus radiation. As will be apparent from anexamination of FIG. 4, the vanes of the offfocus collimation system 25confine the X-ray beam to one including on-focus radiation from thefocal point 13, and a bare minimum of off-focus radiation. Thisarrangement not only substantially confines the off-focus radiation area16 to that of the examination area 15, but also greatly reduces theamount of off-focus radiation which falls within the examination area15. Accordingly, the patient is exposed to less radiation, and theresulting radiograph has a sharper and more read able image. v

Although the invention has been described in its preferred form with acertain degreeof particularity, it is understood that the presentdisclosure of the preferred form has been made only by way of exampleand that numerous changes in the details of construction and thecombination and arrangement of parts may be resorted to withoutdeparting from the spirit and the scope of the invention as hereinafterclaimed.

What is claimed is:

1. A radiation collimator comprising, in combination;

a. an X-ray source for directing a beam of X- radiation along a beampath;

b. on-focus diaphragm means for rectangularly delineating the beam;

c. off-focus collimation mean interposed between said source and saidon-focus diaphragm means for blocking off-focusradiation, and including:

i. two pairs of opposed diaphragm structures interconnected with saidon-focus diaphragm means for concurrent movement therewithtorectangularly delineate the X-ray beam;

ii. each of said diaphragm structures including a plurality of vanessupported at locations spaced longitudinally along the beam path andbeing movable as a unit toward and away from the beam path;

iii. the vanes of one pair of diaphragm structures being interleavedwith the vanes of the other pair of diaphragm structures and vbeingmovable in- 7 wardly and outwardly thereof independently of the positionof said other pair of diaphragm structures.

2. The radiation collimator of claim 1 wherein:

a. each of said diaphragm structures further includes a supporting stemextending generally axially along the beam path and mounting said vanes;

b. said stem being movable mounted for moving said vanes transversely ofthe beam path.

3. The radiation collimator of claim 2 wherein:

a. said stems are pivotally mounted about axes spaced from said X-raysource; and,

b. said vanes are mounted on said stems at locations intermediatesaidaxes and said source.

.4. The radiation collimator of claim 3 wherein such ones {of said vanesas are positioned nearest to the radiation source are configured suchthat their inner beam delineating edges remain at a substantiallyconstant distance from the X-ray source as said nearest vanes arepivoted inwardly and outwardly toward and away from the beam path.

5. The radiation collimator of claim 3 wherein all of said vanes haveinner beam delineating edges defined by the inner sides of the vanes andthe upper surfaces of the vanes, and the inner sides are inclined awayfrom the beam path to prevent their being struck by radiation.

6. A radiation collimator for collimating a radiation beam emanatingfrom the focal point of a radiation source and traversing a beam path,comprising:

a. diaphragm means movably positioned along the beam path fordelineating'the perimeter of the beam to a first cross-sectionalsize andconfiguration;

b. off-focus radiation collimation means positioned between saiddiaphragm means and the radiation source at a location near theradiation source and including movable means for blocking off-focusradiation emanating from points within said source other than said focalpoint, said movable means serving to delineate the beam perimeter to asecond cross-sectional size and configuration which proportionally;corresponds to' said first crosssectional size and configuration;

c. said movable means including a plurality of movably mounted stemseach rigidly supporting aplurality of vanes for movement as a unittoward and away from the beam path with the vanes supported by adjacentstems being interleaved; and,

d. connection means operably interconnecting said diaphragm means andsaid movable means for concurrently moving saiddiaphragm. means and saidmovable means toward and away from said beam axis whereby the beamperimeter delineated by said diaphragm means and said movable meansproportionally decreases or increases in size, and

the first and second cross-sectional configurations continueto-proportionally correspond.

7. The radiation. collimator of claim 6 wherein said vanes are supportedcentrally on their respective stems and said stems extend generallyaxially along the beam bath and are movable to position said vanestransve rsely of the beam path.

8. The radiation collimator of claim 7 wherein the outer sides of saidvanes are curved to give the assembled vane array a generally circularcross section.

versely of the beam path.

9. The radiation collimator of claim 7 wherein said stems are pivotallymounted .forpivoting said vanes through an arc to effect positioning ofsaid vanes trans- 10. The radiation collimator of claim 9 wherein saidstems are mounted for pivotal movement about axes extending generallyparallel to the longitudinal dimension of said vanes, said axes beingspaced from such ones of said vanes as are adapted to extend in closestproximity to the radiation source. a

11. The radiation collimator-of claim 10 wherein said ones of said vanesare smaller in cross-sectional area than others of said vanes.

' 12. The radiation collimator of claim 7 wherein such ones of saidvanes as are adapted to be positioned nearest to the radiation sourceare configured such that the inner beam delineating edges remain at asubstantially constant distance from the X-ray source as said nearestvanes are pivoted inwardly and outwardly toward and away from the beampath.

13. A radiation collimator a radiation beam emanating from a radiationsource and along abeam path comprising:

a. diaphragm means positioned along the beam path for delineating theperimeter of the beam;

b. off-focus radiation collimation means positioned between saiddiaphragm means and the radiation source at a location near theradiation source comprising:

i. opposed pairs of diaphragm structures, the diaphragm structures ofeach. pair being intercon-' 1 nected for concurrent movement toward andaway from the beam path;

ii. each of said diaphragm structures including an array of vanesmovable together as a unit toward and away from the beam path; iii. thevanes of one pair of diaphragm structures being interleaved with thevanes of adjacent diaphragm structures; and, (1. connection meansinterconnecting said diaphragm means and said opposed pairs of diaphragmstructures for concurrent movement toward and away from the beam axis.

14. The radiation collimator of claim 13 comprising two pairs of opposeddiaphragm structures, the vanes of one of said pairs of diaphragmstructures being interleaved with the vanes of the other of said pairsof diaphragm structures.

15. The radiation collimator of claim 14 wherein the outer sides of saidvanes arecurved to give the assem- 18. The radiation collimator of claim16 wherein the vanes supportedon each stem are of increasing length andcross-sectional area the farther removed they are from the X-ray source.

19. The radiation collimator of claim 18 wherein the vanes nearest theX-ray source are configured such that their inner beam delineating edgesremain at a substantially constant distance from the X-ray source assaid nearest vanes are pivoted inwardly and outwardly toward and awayfrom the beam path.

20. The radiation collimator of claim 19 wherein all of said vanes haveinner beam delineating edges defined by the inner sides of the vanes andthe upper surfaces of the vanes, and the inner sides are inclined awayfrom the beam path to prevent their being struck by radiation.

21. In an X-ray apparatus having a source of X- radiation positioned todirect a beam of X-rays emanating from a focal point along a path towarda subject, the improvement of a collimator disposed along the beam pathfor collimating the beam comprising:

a. a housing structure;

b. on-focus collimation means movable positioned within said housingstructure at a position spaced from the source of X-radiation foradjustably delineating the perimeter of the X-ray beam at spacedlocations along the beam path;

0. off-focus collimation means movably carried by said housing structureat a position between said on-focus collimation means and the source ofX- radiation and operably coupled to said on-focus collimation means formovement therewith;

d. said off-focus collimation means comprising:

i. two pairs of opposed diaphragm structures;

ii. connection means interconnecting the diaphragm structures of eachpair for concurrent movement toward and away from the beam path;

iii. each of said diaphragm structures carrying a plurality of diaphragmplate means movable together as a unit toward and away from the beampath;

iv. the plate means of one pair of diaphragm structures beinginterleaved with the plate means of the other pair of diaphragmstructures at axially spaced positions along the beam path wherebyeither pair of diaphragm structures can be moved toward or away from thebeam path independently of and without interfering with the operation ofthe other pair of diaphragm structures.

22. The X-ray apparatus of claim 21 wherein the diaphragm structures ofat least one of said pairs each includes a supporting stem which extendstransversely of the associated plate means, and said plate meanscomprise an array of plates supported on said stem.

23. The X-ray apparatus of claim 22 wherein said array of platesincludes plates centrally mounted on said stem.

24. The X-ray apparatus of claim 21 wherein all of said diaphragmstructures include a supporting stem extending transversely of saidplate means, and said plate means comprises an array of plates supportedon said stems.

25. The X-ray apparatus of claim 24 wherein said plates of one of saidpairs of diaphragm structures is interleaved with the plates of saidother pair of diaphragm structureson a one-to-one basis.

latent No.

UNITED STA'lES PATENT or m F,- (j E RT F [GATE 0 F CO R RE (LTLO N3,829,701 Dated August 13, 1974 Michael Hura Invnntofls) It is curlgil'iud that error appears in tho :xhovv-idmitfjfiud patunt and Lhat saidLetters Patent are hereby corrected us; showrfihel'owz Column 4, line 53, delete "3" and substitute 2 Signed 'and'sealed this 5th day' ofNovember 1974.

(SEAL) Attest: MCCOY M. GIBSON-JR. c. MARSHALL DANN Attesting OfficerCommissioner of Patents USCOMM-DC GO376-r'69 rn t nun-.ua-Lu 'ORMPO-10SO(10-69)

1. A radiation collimator comprising, in combination; a. an X-ray sourcefor directing a beam of X-radiation along a beam path; b. on-focusdiaphragm means for rectangularly delineating the beam; c. off-focuscollimation mean interposed between said source and said on-focusdiaphragm means for blocking off-focus radiation, and including: i. twopairs of opposed diaphragm structures interconnected with said on-focusdiaphragm means for concurrent movement therewith to rectangularlydelineate the X-ray beam; ii. each of said diaphragm structuresincluding a plurality of vanes supported at locations spacedlongitudinally along the beam path and being movable as a unit towardand away from the beam path; iii. the vanes of one pair of diaphragmstructures being interleaved with the vanes of the other pair ofdiaphragm structures and being movable inwardly and outwardly thereofindependently of the position of said other pair of diaphragmstructures.
 2. The radiation collimator of claim 1 wherein: a. each ofsaid diaphragm structures further includes a supporting stem extendinggenerally axially along the beam path and mounting said vanes; b. saidstem being movable mounted for moving said vanes transversely of thebeam path.
 3. The radiation collimator of claim 2 wherein: a. said stemsare pivotally mounted about axes spaced from said X-ray source; and, b.said vanes are mounted on said stems at locations intermediate said axesand said source.
 4. The radiation collimator of claim 3 wherein suchones of said vanes as are positioned nearest to the radiation source areconfigured such that their inner beam delineating edges remain at asubstantially constant distance from the X-ray source as said nearestvanes are pivoted inwardly and outwardly toward and away from the beampath.
 5. The radiation collimator of claim 3 wherein all of said vaneshave inner beam delineating edges defined by the inner sides of thevanes and the upper surfaces of the vanes, and the inner sides areinclined away from the beam path to prevent their being struck byradiation.
 6. A radiation collimator for collimating a radiation beamemanating from the focal point of a radiation source and traversing abeam path, comprising: a. diaphragm means movably positioned along thebeam path for delineating the perimeter of the beam to a firstcross-sectional size and configuration; b. off-focus radiationcollimation means positioned between said diaphragm means and theradiation source at a location near the radiation source and includingmovable means for blocking off-focus radiation emanating from pointswithin said source other than said focal point, said movable meansserving to delineate the beam perimeter to a second cross-sectional sizeand configuration which proportionally corresponds to said firstcross-sectional size and configuration; c. said movable means includinga plurality of movably mounted stems each rigidly supporting a pluralityof vanes for movement as a unit toward and away from the beam path withthe vanes supported by adjacent stems being interleaved; and, d.connection means operably interconnecting said diaphragm means and saidmovable means for concurrently moving said diaphragm means and saidmovable means toward and away from said beam axis whereby the beamperimeter delineated by said diaphragm means and said movable meansproportionally decreases or increases in size, and the first and secondcross-sectional configurations continue to proportionally correspond. 7.The radiation collimator of claim 6 wherein said vanes are supportedcentrally on their respective stems and said stems extend generallyaxially along the beam bath and are movable to position saId vanestransversely of the beam path.
 8. The radiation collimator of claim 7wherein the outer sides of said vanes are curved to give the assembledvane array a generally circular cross section.
 9. The radiationcollimator of claim 7 wherein said stems are pivotally mounted forpivoting said vanes through an arc to effect positioning of said vanestransversely of the beam path.
 10. The radiation collimator of claim 9wherein said stems are mounted for pivotal movement about axes extendinggenerally parallel to the longitudinal dimension of said vanes, saidaxes being spaced from such ones of said vanes as are adapted to extendin closest proximity to the radiation source.
 11. The radiationcollimator of claim 10 wherein said ones of said vanes are smaller incross-sectional area than others of said vanes.
 12. The radiationcollimator of claim 7 wherein such ones of said vanes as are adapted tobe positioned nearest to the radiation source are configured such thatthe inner beam delineating edges remain at a substantially constantdistance from the X-ray source as said nearest vanes are pivotedinwardly and outwardly toward and away from the beam path.
 13. Aradiation collimator a radiation beam emanating from a radiation sourceand along a beam path comprising: a. diaphragm means positioned alongthe beam path for delineating the perimeter of the beam; b. off-focusradiation collimation means positioned between said diaphragm means andthe radiation source at a location near the radiation source comprising:i. opposed pairs of diaphragm structures, the diaphragm structures ofeach pair being interconnected for concurrent movement toward and awayfrom the beam path; ii. each of said diaphragm structures including anarray of vanes movable together as a unit toward and away from the beampath; iii. the vanes of one pair of diaphragm structures beinginterleaved with the vanes of adjacent diaphragm structures; and, d.connection means interconnecting said diaphragm means and said opposedpairs of diaphragm structures for concurrent movement toward and awayfrom the beam axis.
 14. The radiation collimator of claim 13 comprisingtwo pairs of opposed diaphragm structures, the vanes of one of saidpairs of diaphragm structures being interleaved with the vanes of theother of said pairs of diaphragm structures.
 15. The radiationcollimator of claim 14 wherein the outer sides of said vanes are curvedto give the assembled array of said diaphragm structures a generallycircular cross section.
 16. The radiation collimator of claim 13 whereineach diaphragm structure further includes a stem which supports eachvane of said array of vanes at a location centrally of said vanes. 17.The radiation collimator of claim 16 wherein said stems are pivotallymounted.
 18. The radiation collimator of claim 16 wherein the vanessupported on each stem are of increasing length and cross-sectional areathe farther removed they are from the X-ray source.
 19. The radiationcollimator of claim 18 wherein the vanes nearest the X-ray source areconfigured such that their inner beam delineating edges remain at asubstantially constant distance from the X-ray source as said nearestvanes are pivoted inwardly and outwardly toward and away from the beampath.
 20. The radiation collimator of claim 19 wherein all of said vaneshave inner beam delineating edges defined by the inner sides of thevanes and the upper surfaces of the vanes, and the inner sides areinclined away from the beam path to prevent their being struck byradiation.
 21. In an X-ray apparatus having a source of X-radiationpositioned to direct a beam of X-rays emanating from a focal point alonga path toward a subject, the improvement of a collimator disposed alongthe beam path for collimating the beam comprising: a. a housingstructure; b. on-focus collimation means movable positioned within saidhousing structure at a positioN spaced from the source of X-radiationfor adjustably delineating the perimeter of the X-ray beam at spacedlocations along the beam path; c. off-focus collimation means movablycarried by said housing structure at a position between said on-focuscollimation means and the source of X-radiation and operably coupled tosaid on-focus collimation means for movement therewith; d. saidoff-focus collimation means comprising: i. two pairs of opposeddiaphragm structures; ii. connection means interconnecting the diaphragmstructures of each pair for concurrent movement toward and away from thebeam path; iii. each of said diaphragm structures carrying a pluralityof diaphragm plate means movable together as a unit toward and away fromthe beam path; iv. the plate means of one pair of diaphragm structuresbeing interleaved with the plate means of the other pair of diaphragmstructures at axially spaced positions along the beam path wherebyeither pair of diaphragm structures can be moved toward or away from thebeam path independently of and without interfering with the operation ofthe other pair of diaphragm structures.
 22. The X-ray apparatus of claim21 wherein the diaphragm structures of at least one of said pairs eachincludes a supporting stem which extends transversely of the associatedplate means, and said plate means comprise an array of plates supportedon said stem.
 23. The X-ray apparatus of claim 22 wherein said array ofplates includes plates centrally mounted on said stem.
 24. The X-rayapparatus of claim 21 wherein all of said diaphragm structures include asupporting stem extending transversely of said plate means, and saidplate means comprises an array of plates supported on said stems. 25.The X-ray apparatus of claim 24 wherein said plates of one of said pairsof diaphragm structures is interleaved with the plates of said otherpair of diaphragm structures on a one-to-one basis.